Υπολογισμός Δείκτη Διακινδύνευσης έναντι πυρκαγιάς για επιβατηγά πλοία

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Ναυτική και Θαλάσσια Τεχνολογία και Επιστήμη

Αξιολόγηση μηχανισμών ασφάλειας στο έξυπνο δίκτυο διανομής της ηλεκτρικής ενέργειας

Ο στόχος της εργασίας αυτής είναι να συλλέξει, να αναλύσει και να αξιολογήσει λύσεις και ερευνητικές εργασίες σχετικές με το αντικείμενο της ασφάλειας στο έξυπνο δίκτυο διανομής της ηλεκτρικής ενέργειας. Το επίκεντρο αποτέλεσαν εργασίες που χρησιμοποιούν το trusted computing ως τον τρόπο για να επιτύχουν ένα υψηλότερο επίπεδο ασφάλειας, το οποίο και απαιτείται στο έξυπνο δίκτυο διανομής της ηλεκτρικής ενέργειας. Πιο συγκεκριμένα, συλλέχθηκε και αξιολογήθηκε ένα σύνολο εργασιών. Για αυτόν τον σκοπό, οι κύριοι στόχοι των προτεινόμενων λύσεων αναλύθηκαν. Υλοποιήθηκε μια συγκριτική ανάλυση που τονίζει τα πλεονεκτήματα και τα μειονεκτήματα της κάθε λύσης. Βάσει αυτής της σύγκρισης, αξιολογήθηκαν τα αποτελέσματα της κάθε λύσης και δόθηκαν κατευθυντήριες γραμμές για μελλοντικές εργασίες. Συνοψίζοντας, οδηγηθήκαμε στο συμπέρασμα ότι απαιτείται περισσότερη έρευνα στον τομέα της ασφάλειας του έξυπνου δικτύου διανομής της ηλεκτρικής ενέργειας, καθότι μέσω της αξιολόγησης που πραγματοποιήθηκε αποκαλύφθηκε ότι η πλειοψηφία των λύσεων που βρέθηκαν έχουν αδυναμίες είτε από πλευράς ασφάλειας ή από πλευράς επιδόσεων. Επιπρόσθετα, τονίστηκε ότι καθώς οι απαιτήσεις για το έξυπνο δίκτυο διανομής της ηλεκτρικής ενέργειας διαφέρουν από χώρα σε χώρα, καθίστανται αναγκαία η ύπαρξη διεθνών προτύπων. Είναι πεποίθησή μας πως μόνο μετά από μια συνολική επισκόπηση των χαρακτηριστικών του έξυπνου δικτύου διανομής της ηλεκτρικής ενέργειας, τα ζητήματα που προκύπτουν αναφορικά με την ασφάλεια μπορούν να ταυτοποιηθούν και να επιλυθούν με αποτελεσματικό τρόπο.The purpose of this thesis is to collect, analyze and evaluate solutions and research works relevant to the subject of security in smart grid. The focus was on the works that use trusted computing as a way to achieve a higher level of security which is required in smart grid. More specifically, we collected and reviewed a set of papers. To this end, the main goals of the proposed solutions were analyzed. We performed a comparative analysis highlighting the advantages and drawbacks of each solution. Based on this comparison, we evaluated the results of each solution and provided guidelines for the future work. As a generic conclusion, we deduced that more research is required in the field of smart grid security since our evaluation revealed that the majority of the solutions have weak points either from a security or performance point of view. Moreover, we pinpointed that as the standards for the smart grid are different between countries, there is also a need for standardization activities. We believe that only after a uniform view of the smart grid specifications, security issues can be identified and resolved effectively

Energy and economic evaluation of a solar assisted ground source heat pump system for a north Mediterranean city

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.In this study, a PVT based solar assisted ground source heat pump (SAGSHP) system was investigated regarding its energy performance and cost-effectiveness for the city of Thessaloniki (Greece). The SAGSHP system was set up to cover the space heating and domestic hot water needs for a low-rise dwelling. A mathematic model of the system was formulated in TRNSYS was used with the aim to carry out parametric analysis by varying the number of the PVTs. Two of the most important components of the employed model, the PVT collector and the geothermal heat exchanger, have already been validated via experimental data. Simulations were conducted and through the results seven energy metrics were estimated, with the objective to examine the system’s energy performance from various perspectives. The SAGSHP system with 16 PVTs was found capable of covering 73 % of the heating load and to generate 1.22 times more electricity than that consumed by the system. The electricity yield of PVTs was not affected throughout the parametric analysis, and the maximum specific productivity was estimated at 301.5 kWhe PVT-1 per year. The results suggest that a SAGSHP system equipped with about 14 PVTs can reach energy self-sufficiency. As regards the economics of the SAGSHP system, this was compared with a natural gas boiler system via two methods: life cycle cost (LCC) and life cycle savings (LCS). A sensitivity analysis with major economic parameters of the systems was carried out. It was found that the cost-effectiveness of the SAGSHP system is influenced mainly by its capital cost and by the price of the natural gas. Systems equipped with less than 12 PVTs can be cost-competitive by subsiding from 8 % up to 42 % of their capital cost. Also, system with more than 12 collectors were found of more benefit than the smaller ones, in the case where feed-in-tariff schemes are applied, or the bank loan’s interest rate is low. It can be concluded that, the proposed system can be an attractive monetary solution for covering the heating load in comparable dwellings with a similar climate to Thessaloniki

Long-term sea surface temperature variability in the Aegean Sea

The inter-annual/decadal scale variability of the Aegean Sea Surface Temperature (SST) is investigated by means of long-term series of satellite-derived and in situ data. Monthly mean declouded SST maps are constructed over the 1985–2008 period, based on a re-analysis of AVHRR Oceans Pathfinder optimally interpolated data over the Aegean Sea. Basin-average SST time series are also constructed using the ICOADS in situ data over 1950–2006. Results indicate a small SST decreasing trend until the early nineties, and then a rapid surface warming consistent with the acceleration of the SST rise observed on the global ocean scale. Decadal-scale SST anomalies were found to be negatively correlated with the winter North Atlantic Oscillation (NAO) index over the last 60 years suggesting that along with global warming effects on the regional scale, a part of the long-term SST variability in the Aegean Sea is driven by large scale atmospheric natural variability patterns. In particular, the acceleration of surface warming in the Aegean Sea began nearly simultaneously with the NAO index abrupt shift in the mid-nineties from strongly positive values to weakly positive/negative values

Optimal Financial Insulation Thickness of a Broiler House

A common method for environmental control in livestock facilities is to use thermal insulation for exterior walls and roof. In regions with cool winters increasing the insulation thickness decreases the heating requirements, however in regions with hot summers may lead to unwanted increase of inside temperature, thus intensifying cooling loads. It is worth noting that financial thickness optimization of a broiler house external walls and gable roofs insulation for different orientations has not been sufficiently addressed, thus a detailed transient simulation was used to model existing energy audited broiler house and to calculate its annual heating and cooling loads. For that, hourly climatic data and all the heat and moisture gains and losses resulting from birds, heat flow through the building envelope and ventilation were taken into account. An economic analysis based on the Life Cycle Savings (LCS) method was performed for the walls and gable roofs for various insulation thicknesses and orientations. The comparison of the annual heating load per unit area with that of similar energy audited broiler houses was satisfactory. The optimum insulation thickness of external walls and gable roofs was found to be between 4.0 cm and 4.5 cm depending on their orientation, while the wall facing north offered the greatest economic benefit compared to other orientations. According to the results, the annual cooling load was 3.3 times higher than that of heating

A Multi-Parametric Mathematical Approach on the Selection of Optimum Insulation Thicknesses in Buildings

Detailed simulations have indicated optimum insulation thicknesses of walls’ insulation for a variety of cases. Simplified analytical relations have also been proposed to the same aim, allowing the extraction of more general results, with limited accuracy however, as imposed by mathematical simplicity requirements. In this sense, a variety of important parameters are ignored, such as: the existence of any glazing at the wall, the absorptance of the wall, the base temperature of the heated space which the referred to wall belongs to and its variation with insulation, the thermal characteristics (thermal capacitance, total heat losses coefficient) and the heat and solar gains of the heated space. An alternative analytical approach is consequently developed here, incorporating all above parameters and in this context accessing the wall as part of the whole heated space, instead of considering it solely as an isolated fabric element. The approach consists of a set of two implicit equations which are easily solved, and enables the investigation of the effects of all principal and secondary parameters on the optimum thickness. The ignorance even of the secondary of these parameters has proved to lead to significant errors

Optimal economic thickness of various insulation materials for different orientations of external walls considering the wind characteristics

The economic optimum insulation thickness of various insulation materials for external walls of different topologies and orientations was determined, taking into account the heating and cooling period and the speed and direction of the wind. Annual heating and cooling transmission loads are being calculated based on transient heat flow through the external walls and by using hourly climatic data for an entire typical meteorological year of the city of Larnaca, Cyprus. The available wind speed and direction data have been statistically analysed for the assessment of the prevalent wind directions in the area. The optimisation is carried out using the Life Cycle Savings method. According to the results, the north-facing walls offer the greatest economic benefit compared to the corresponding wall types of different orientation, regardless of the insulation thickness. They also have the shortest payback period. The optimum insulation thickness calculated for any wall topology and orientation varies from 4.25 cm to 15.5 cm, and the payback period varies from 5.47 years to 12.11 years

Wind energy potential assessment in Naxos Island, Greece

The current paper presents an investigation of the wind power potential of Koronos village, a remote location in the northeastern part of Naxos Island, Greece, using real wind data by a measurement mast. The obtained wind characteristics were statistically analysed using the Weibull and Rayleigh distribution functions. The results from this investigation showed that the selected site falls under Class 7 of the international system of wind classification as the mean annual wind speed recorded in the area was 7.4 m/s and the corresponding annual mean power density was estimated to be 420 W/m2. Furthermore, the prevailing wind directions characterising the area were the northeastern and the north–northeastern. From the statistical analysis of these results, it was revealed that the Weibull model fitted the actual data better. This remark was further enhanced by the evaluation of the performance of these two distribution